Lead Poisoning and The Bell Curve

Abstract

A robust environmental health literature demonstrates that preschool lead exposure can cause neurodevelopmental damage and associated adverse impacts on IQ, education, and behavior. Cognitive psychology research also shows an association between IQ and education and behavior risks, but finds that IQ is largely inherited. The impact of lead exposure was barely acknowledged in a fierce debate over IQ after the 1994 publication of The Bell Curve, but subsequent research has shown that trends in behavior linked to IQ in The Bell Curve have tracked lead exposure trends across decades and around the world. Preschool lead exposure trends continue to predict global crime trends and USA trends in education attainment, mental retardation, and teenage pregnancy. Evidence from temporal analyses and other lead toxicity research suggest a causal relationship between lead exposure and important societal trends. Trends in tooth enamel formed in early childhood also confirm that The Bell Curve reflected birth years of extreme variation in lead exposure, resulting in extreme differences in estimated behavior risks associated with IQ. This evidence also presents a new perspective on cognitive research indicating that IQ is inherited.